How the UK’s weather can affect and degrade stone buildings and facades

The UK was the first country in the world to declare climate change as a national emergency. So, with COP26 at the forefront of our minds, today we are looking at how dramatic shifts in weather conditions are having a major impact on the buildings we live and work in – especially those made of stone.

Stone has a reputation for being highly robust; it has been used in construction since 9,000 BC when ancient architects of the time built the great Gobekli Tepe in south-eastern Turkey. Pre-dating Stonehenge by a whopping 6,000 years, the Gobekli Tepe still stands today as a testament to the durability and longevity of the limestone it was constructed from.

The natural mineral properties of stone give it strength and durability to survive relatively unscathed for long periods of time, but that doesn’t make it immune to harsh weather conditions.

Just like wood, stone is known to expand and shrink in different temperatures. But as our weather becomes more extreme and the seasons more intense, it’s only a matter of time before we could see stone buildings falling to ruins due to these ultra-harsh environmental factors that were previously unheard of.

Stone discolouration

Discolouration is a serious problem that affects most stone buildings over time. It can be caused by the effects of intense UV radiation, air pollution, or weathering – as in the case of the Taj Mahal.

One of the seven wonders of the world, the marble façade on the Taj Mahal has changed its colour from white to yellow to a greenish tint in the past few years due to the emissions from the oil refineries in Mathura (a city that’s 40kms from the monument).

These emissions contain sulphur dioxide, nitrogen dioxide, and carbon particles which mix with the atmosphere to cause acid rain. This has been cited as the main reason behind the Taj’s unfortunate discolouration.

Discolouration can also happen if poor quality material is used in construction. But in the case of the Taj, architect Shah Jahan spared no expense on this magnificent building, using Makrana marble which contains only 2% impurities – the other 98% of which is calcium carbonate.

Even as close to home as London, See Brilliance operatives regularly work on projects involving the restoration of discoloured stone which is, in many cases, caused by similar events experienced by the Taj Mahal: local pollution and bad weather.

Stone dullness

Technically, dullness is hard to define but suffice it to say that dullness makes the stone surface look greyish, less colourful, and sometimes more porous or even powdery.

Dullness on a stone façade can be caused by a number of factors including a lack of proper cleaning and the environment in which the building is situated. It can even occur due to acid etching of the surface of the stone primarily caused by the sulphur dioxide gases emitted in the air.

Excessive exposure to acid rain can also cause pitting of the stone, which can lead to further degradation and damage.

Algae growth on stone

The UK climate is especially beneficial for algae and other biological growth on building facades. Stone is particularly vulnerable to biological growth because it retains water which can encourage bacteria, algae, fungi, and even moss to grow on any stone building façade.

Historic England says that, while organic growths contribute to the natural, aged patina that gives masonry its appealing aesthetic on historic structures, if left untreated it can damage masonry and cause deterioration.

Changes in our climate, particularly in temperature and the frequency or intensity of rainfall, are resulting in an observed increase in ‘greening’, indicating more active algal colonisation.

Our operatives frequently see this type of issue and are fully equipped to deal with it using the DOFF Steam Cleaning system which will remove algae, fungi and other biological matter and will kill off spores. This means there is no need to use a chemical biocide during the removal process or as a protection against further biological activity. The system is both safe for the stone surface and highly effective at removing algae and most other biological contaminants and does not over wet the substrate.

Given the current unpredictability of our weather conditions, we expect this issue to become much more prevalent in the months and years to come.

Cracks and gaps in stone

Stone has historically been favoured by builders and architects because of its general resilience and ability to resist harsh weather conditions. But it isn’t invincible.

Any stone building can be damaged by constant exposure to wet weather that’s caused by prolonged rainy seasons. The freezing and thawing caused by water penetration and evaporation during the winter months can loosen mortar. This freeze-thaw cycle often leads to cracks and gaps that grow over time.

In 2011, scientists from the Met Office reported that our warmer atmosphere was holding more moisture than ever before. The report concluded that water vapour increases by 7% for every degree centigrade of warming.

This year, the Met Office has confirmed that in the next 50 years (by 2070), winter will be up to 30% wetter while summer will be up to 60% drier.

The repercussions for our stone architecture could be very severe as it means stone buildings could be exposed to three months of constant, heavy rain and three months of complete dryness, leading to stone damage and degradation caused by excessive water evaporation.

Water evaporation

Water evaporation can cause stone to lose moisture and become brittle. What makes this process dangerous is that as water evaporates it leaves behind salts and minerals such as sulphates, chlorides, sodium carbonate, and nitrates. When these minerals dry, they form salt stains on the surface of the stone which breaks down larger pieces of stone to form spalls.

These mineral deposits settle in the cracks and gaps created by water penetration in the rainy season and deteriorate the quality of the masonry over time.

A combination of colder, wetter winters and dryer, hotter summers could see stone surfaces become damaged by repeat cycles of excess water evaporation and subsequent extreme dryness.

Crystallisation of stone

Stone crystallisation refers to the formation of crystals in the stone’s pores, causing it to degrade or disintegrate. This is a normal process that occurs when stone is exposed to rain, snow, or frost.

Stones that are crystallised almost always lose their integrity and chemical stability which can lead to stone weathering.

Researchers call this process “supersaturation”, saying that the supersaturation of salt in stone buildings can worsen in extreme cold.

The research, which was published in 2014, said that during temperate cycles in which the temperature never fell below 25 ˚C (77˚ F), it took an average of four cycles before damage to stone occurred. When the temperature dropped to 3˚ C (37˚ F), one cycle was enough.

Keeping the UK’s stone buildings strong and healthy

As you can see, all types of seasons, temperatures, and climate conditions together contribute to the deterioration of one of the strongest building materials available. But preventative measures can help.

At See Brilliance, we have more than 30 years’ experience working with building owners across the UK. Our team of operatives are experienced in stone restoration, façade restoration, cleaning and restoring historic buildings and landmarks. Discover more about how we can safely remove graffiti, restore stone, restore glass façades, clean concrete residue, and restore all types of building façade and cladding so that your buildings last longer without losing their glory.

See Brilliance specialises in restorative commercial cleaning of metal, glass and stone. We also provide commercial façade restoration, stone façade restoration, glass façade restoration, TORC Cleaning, graffiti removal, and much more, all across the UK.

If you’d like to get in touch today, call our team directly on 01635 230 888 or email info@seebrilliance.com.

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